Nearby star 'a good candidate for Earth'

TAU Ceti, one of our closest stars, is a good candidate for hosting an Earth-like planet, astronomers say.

Located 12 light years away, the Sun-like star has five planets in orbit in a balmy zone which gives the best chance for nurturing life, they say.

One of the planets has a mass about five times that of the Earth, making it the smallest planet found so far in this vital zone, they said.

About 800 exoplanets - worlds orbiting stars other than our own - have been spotted since 1995.

But none is a home from home. These planets are either uninhabitable gas giants or are big rocky worlds that swing so close to their star they are literally roasted.

The quest is to find a rocky planet that is not only close to the mass of Earth but is also located in the so-called "Goldilocks zone".

This is an orbital distance from the star where temperature is neither too hot nor too cold, but just right to sustain liquid water, which is essential for life as we know it.

The Tau Ceti finding was made by astronomers from Australia, Britain, Chile and the United States, who applied a new technique to filter data from more than 6000 observations.

By doing so, they believe they have eliminated distorting signals, called "noise", that mask the existence of low-mass planets.

They applied the technique to light from Tau Ceti, to determine it is not a lone star but in fact one with a planetary system.

"This discovery is in keeping with our emerging view that virtually every star has planets, and that the galaxy must have many such potentially habitable Earth-sized planets," said Steve Vogt, a veteran exoplanet-hunter.

"We are now beginning to understand that Nature seems to overwhelmingly prefer systems that have multiple planets with orbits of less than one hundred days."

"This is quite unlike our own solar system. So our solar system is, in some sense, a bit of a freak."

On October 17, European astronomers reported they had detected a planet with about the mass of Earth orbiting Alpha Centauri B, which is only 4.3 light years away.

However, the planet itself is not "another Earth" as it is not in the Goldilocks zone. It zips around the star at a scorchingly close distance, and liquid water could not exist there.

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